Workers in this unit group erect and operate drilling plant and perform related tasks in the sinking and operation of wells. Their functions include: preparing and operating derrick pipe-handling devices and slush pumps; operating rotary or percussion drilling plant to drill oil or gas wells; cementing openings in walls or casings of oil or gas wells; cleaning and servicing oil or gas wells and repairing and replacing pumping rods, casings and tubings; treating oil and gas wells with acid to increase their production; setting up and operating drilling plant to drill wells or bores other than for oil or gas; performing related tasks.